The following Patent Documents 1 and 2 disclose conventional tool holders used to hold rotary cutting tools.
The tool chuck disclosed in Patent Document 1 includes a chuck cylinder having a tool holding hole and a tapered outer peripheral surface, and a nut (tightening cylinder) mounted around the chuck cylinder through needle rollers. By tightening the nut, the chuck cylinder is radially compressed, so that a tool inserted in the tool holding hole can be securely held in position.
The chuck device disclosed in Patent Document 2 is a hydraulic chuck, wherein an elastically deformable sleeve is liquid-tightly fitted in a tapered inner peripheral portion having an opening at the front end of the body to define expansion rooms between the sleeve and the inner peripheral surface of the body. Hydraulic pressure is applied to the expansion rooms to diametrically compress the sleeve so that a tool inserted in the hole of the sleeve is securely held in position.